The generation of toxic reduction products of oxygen within the active site of cytochrome oxidase is the most well-regulated source of intracellular pollution by radical species of oxygen reduction. The nature of the pocket in the cytochrome oxidase molecule and the nature of the toxic oxygen reduction products that are formed within this pocket are important in evaluating how they are dealt with in the respiration of isolated mitochondria and intact tissues. The goals of the project are thus to establish basic principles by which cytochrome oxidase deals with the toxic products of oxygen reduction and to develop a rationale for the handling of toxic substances upon the delivery of oxygen from lung to organs of the body which may be damaged in the process, especially the lung. Techniques are to be developed and employed for this study, particularly optical spectrophotometry combined with X-ray edge absorption of the copper and iron components of cytochrome oxidase.